Soybean cultivar S73-Z5

ABSTRACT

The invention is a novel soybean cultivar designated S73-Z5 with high yield potential and tolerance to Roundup herbicide. The invention relates to seeds of the cultivar S73-Z5, plants of the cultivar S73-Z5, and to methods for producing a soybean plant produced by crossing the soybean S73-Z5 by itself or another soybean genotype.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinctive soybean cultivar, designated S73-Z5.

There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety an improved combination of desirable traits from the parental germplasm. These important traits may include higher seed yield, resistance to diseases and insects, better stems and roots, tolerance to drought and heat, and better agronomic quality.

Choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of cultivar used commercially (e.g., F₁ hybrid cultivar, pureline cultivar, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection.

The complexity of inheritance influences choice of the breeding method. Backcross breeding is used to transfer one or a few favorable genes for a highly heritable trait into a desirable cultivar. This approach has been used extensively for breeding disease-resistant cultivars. Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination, and the number of hybrid offspring from each successful cross.

Each breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful cultivars produced per unit of input (e.g., per year, per dollar expended, etc.).

Promising advanced breeding lines are thoroughly tested and compared to appropriate standards in environments representative of the commercial target area(s) for three or more years. The best lines are candidates for new commercial cultivars; those still deficient in a few traits may be used as parents to produce new populations for further selection.

These processes, which lead to the final step of marketing and distribution, usually take from eight to 12 years from the time the first cross is made. Therefore, development of new cultivars is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.

A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior plant is to observe its performance relative to other experimental plants and to a widely grown standard cultivar. If a single observation is inconclusive, replicated observations provide a better estimate of its genetic worth.

The goal of a plant breeding is to develop new, unique and superior soybean cultivars and hybrids. The breeder initially selects and crosses two or more parental lines, followed by repeated selfing and selection, producing many new genetic combinations. The breeder can theoretically generate billions of different genetic combinations via crossing, selfing and mutations. The breeder has no direct control at the cellular level. Therefore, two breeders will never develop the same line, or even very similar lines, having the same soybean traits.

Each year, the plant breeder selects the germplasm to advance to the next generation. This germplasm is grown under unique and different geographical, climate and soil conditions, and further selection are then made, during and at the end of the growing season. The cultivars which are developed are unpredictable. This unpredictability is because the breeder's selection occurs in unique environments, with no control at the DNA level (using conventional breeding procedures), and with millions of different possible genetic combinations being generated. A breeder of ordinary skill in the art cannot predict the final resulting lines he develops, except possibly in a very gross and general fashion. The same breeder cannot produce the same cultivar twice by using the exact same original parents and the same selection techniques. This unpredictability results in the expenditure of large amounts of research monies to develop superior new soybean cultivars.

The development of new soybean cultivars requires the development and selection of soybean varieties, the crossing of these varieties and selection of superior hybrid crosses. The hybrid seed is produced by manual crosses between selected male-fertile parents or by using male sterility systems. These hybrids are selected for certain single gene trains such as pod color, flower color, pubescence color or herbicide resistance which indicate that the seed is truly a hybrid. Additional data on parental lines as well as the phenotype of the hybrid influence to breeder's decision whether to continue with the specific hybrid cross.

Pedigree breeding and recurrent selection breeding methods are used to develop cultivars from breeding populations. Breeding programs combine desirable traits from two or more cultivars or various broad-based sources into breeding pools from which cultivars are developed by selfing and selection of desired phenotypes. The new cultivars are evaluated to determine which have commercial potential.

Pedigree breeding is used commonly for the improvement of self-pollinating crops. Two parents which possess favorable, complementary traits are crossed to produce an F₁. An F₂ population is produced by selfing one or several F's. Selection of the best individuals may begin in the F₂ population; then, beginning in the F₃, the best individuals in the families are selected. Replicated testing of families can begin the F₄ generation to improve the effectiveness of seletion for traits with low heritability. At an advanced stage of inbreeding (i.e., F₆ and F₇), the best lines or mixtures of phenotypically similar lines are tested for potential release as new cultivars.

Mass and recurrent selections can be used to improve populations of either self- or cross-pollinating crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued.

Backcross breeding has been used to transfer genes for a simply inherited, highly heritable trait into a desirable homozygous cultivar or inbred line which is the recurrent parent. The source of the trait to be transferred is called the donor parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent. After the initial cross, individuals possessing the phenotype of the donor parent are selected and repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent.

The single-seed descent procedure in the strict sense refers to planting a segregating population, harvesting a sample of one seed per plant, and using the one-seed sample to plant the next generation. When the population has been advanced from the F₂ to the desired level of inbreeding, the plants from which lines are derived will each trace to different F₂ individuals. The number of plants in a population declines each generation due to failure of some seeds to germinate or some plants to produce at least one seed. As a result, not all of the F₂ plants originally sampled in the population will be represented by a progeny when generation advance is completed.

In a multiple-seed procedure, soybean breeders commonly harvest one or more pods from each plant in a population and thresh them together to form a bulk. Part of the bulk is used to plant the next generation and part is put in reserve. The procedure has been referred to as modified single-seed descent or the pod-bulk technique.

The multiple-seed procedure has been used to save labor at harvest. It is considerably faster to thresh pods with a machine than to remove one seed from each by hand for the single-seed procedure. The multiple-seed procedure also makes it possible to plant the same number of seeds of a population each generation of inbreeding. Enough seeds are harvested to make up for those plants that did not germinate or produce seed.

Descriptions of other breeding methods that are commonly used for different traits and crops can be found in several reference books (e.g., Allard, 1960; Simmonds, 1979; Sneep et al., 1979; Fehr, 1987).

Proper testing should detect any major faults and establish the level of superiority or improvement over current cultivars. In addition to showing superior performance, there must be a demand for a new cultivar that is compatible with industry standards or which creats a new market. The introduction of a new cultivar will incur additional costs to the seed producer, the grower, processor and consumer, for special advertising and marketing, altered seed and commercial production practices, and new product utilization. The testing proceeding release of a new cultivar should take into consideration research and development costs as well as technical superiority of the final cultivar. For seed-propagated cultivars, it must be feasible to produce seed easily and economically.

Soybean, Glycine max (L), is an important and valuable field crop. Thus, a continuing goal of plant breeders is to develop stable, high yielding soybean cultivars that are agronomically sound. The reasons for this goal are obviously to maximize the amount of grain produced on the land used and to supply food for both animals and humans. To accomplish this goal, the soybean breeder must select and develop soybean plants that have the traits that result in superior cultivars.

SUMMARY OF THE INVENTION

The invention is a novel soybean cultivar designated S73-Z5 with high yield potential and tolerance to Roundup herbicide. The invention relates to seeds of the cultivar S73-Z5, plants of the cultivar S73-Z5, and to methods for producing a soybean plant produced by crossing the soybean S73-Z5 by itself or another soybean genotype.

DEFINITIONS

In the description and tables which follow, a number of terms are used. In order to provide a clear and consistent understanding of the specification and claims, including to scope to be given such terms, the following definitions are provided:

Maturity Date. Plants are considered mature when 95% of the pods have reached their mature color.

Seed Yield (Bushels/Acre). The yield in bushels/acre is the actual yield of the grain at harvest.

Lodging Resistance. Lodging is rated on a scale of 1 to 9. Where one is completely upright and 9 is completely prostrate.

Emergence. This score indicates the ability of the seed to emerge when planted 3" deep in sand and with a controlled temperature of 25° C. The number of plants that emerge each day are counted. Based on this data, each genotype is given a 1 to 5 score based on its rate of emergence and percent of emergence, an intermediate score of 2.5 indicates average ratings and a 5 score indicates a very poor rate and percent of emergence.

Iron-Deficiency Chlorosis. Plants are scored 1 to 9 based on visual observations. A score of 1 means no stunting of the plants or yellowing of the leaves and a score of 9 indicates the plants are dead or severely stunted due to iron-deficiency chlorosis.

Brown Stem Rot. Plants are scored from 1 to 9 by visually comparing all genotypes in a given test. The score is based on leaf symptoms of yellowing and necrosis caused by brown stem rot. A score of 1 indicates no symptoms. Visual scores range to a score of 9 which indicates severe symptoms of leaf yellowing and necrosis.

Sudden Death Syndrome. Plants are scored from 1 to 9, with 1 indicating no symptoms and 9 indicating severe leaf symptoms.

Shattering. The amount of pod dehiscence prior to harvest. Pod dehiscence involves seeds falling from the pods to the soil. This is a visual scene from 1 to 9 comparing all genotypes within a given test. A score of 1 means pods have not opened and no seeds have fallen out. A score of 9 indicates 100% of the pods are opened.

Plant Height. Plant height is taken from the top of soil to top of node of the plant and is measured in centimeters.

DETAILED DESCRIPTION OF THE INVENTION

Parentage: S 75-55 (2)×(S 59-60 (2)×40-3-2). S 75-55 and S 59-60 are commercial cultivars developed by Novartis (Northrup King). 40-3-2 is a line developed by Monsanto which carries their patented gene conferring tolerance to Roundup Herbicide. Seed of S 59-60 was supplied to Monsanto to make the initial cross to 40-3-2 and one backcross. This BC1F1 was planted at the NK Research Center at Waimea, Kauai, Hi., in December of 1993. F₁ plants were sprayed with Roundup at the vegetative stage to eliminate susceptibles. Surviving plants were used as males to cross to S75-55. This F₁ population, numbered 92303, was planted at Bay, Ariz., in May of 1993. Plants were sprayed with Roundup to remove susceptible plants. Resistant plants were used as males to cross onto S 75-55 to make the BC1 (cross number 93303). F₁ seeds were planted at Waimea in December of 1993. F₁ plants were sprayed with Roundup, and resistant survivors were used as males in making a second backcross onto S 75-55 (cross 94303). Seeds from this BC2F1 cross were planted at Bay in June, 1994. F₁ plants were again sprayed with Roundup and harvested in November, 1994 The BC2F2 population was planted in November at Waimea, sprayed with Roundup at the vegetative stage, and harvested in February by picking 2-3 pods from each resistant plant. The resulting F₃ population was planted at Waimea in March, 1995, and again sprayed prior to flowering. Individual F₃ plants were harvested in May, threshed individually, and grown in plant progeny rows at Bay in the summer of 1995. These progeny rows were sprayed with Roundup and 130 rows were found to be homogeneous for tolerance. These rows were closely monitored for phenotypic similarity to S 75-55. In November, rows which expressed the S 75-55 phenotype were bulked together for further testing and seed increase. This variety was extensively tested in 1996 and released in 1997 as S73-Z5.

Some of the criteria used to select in various generations include; seed yield, lodging resistance, emergence, disease tolerance, maturity, late season plant intactness, plant height and shattering resistance.

The cultivar has shown uniformity and stability for all traits, as described in the following variety description information. It has been self-pollinated a sufficient number of generations, with careful attention to uniformity of plant type to ensure homozygosity and phenotypic stability. The line has been increased with continued observation for uniformity. No variant traits have been observed or are expected in S73-Z5. Soybean cultivar S73-Z5 has the following morphologic and other characteristics:

    ______________________________________     Plant Types & Habit:                    Intermediate                              Flower color:                                          Purple     Hypocotyl Color:                    Dark Purple                              Pod color:  Tan     Leaflet Shape: Ovate     Hilum color:                                          Black     Stem Termination:                    Determinate                              Seed Coat Color:                                          Yellow     Plant Pubescence color:                    Tawny     Cotyledon color:                                          Yellow     Seed Protein Peroxidase                    Negative     Activity:     Phytophthora Res. Gene:     Maturity Group VII     Relative Maturity:                    VII-3     Average Seeds Per Pound:                    2900     ______________________________________

This invention is also directed to methods for producing a soybean plant by crossing a first parent soybean plant with a second parent soybean plant, wherein the first or second soybean plant is the soybean plant from the line S73-Z5. Further, both first and second parent soybean plants may be from the cultivar S73-Z5. Therefore, any methods using the cultivar S73-Z5 are part of this invention; selfing, backcrosses, hybrid breeding, and crosses to populations. Any plants produced using cultivar S73-Z5 as a parent are within the scope of this invention. As used herein, the term "plant" includes plant cells, plant protoplasts, plant cells of tissue culture from which soybean plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants, such as pollen, flowers, seeds, pods, leaves, stems, and the like. Thus, another aspect of this invention is to provide for cells which upon growth and differentiation produce the cultivar S73-Z5.

                                      TABLES     __________________________________________________________________________     S73-Z5 was tested in the NK Advanced Group VII Yield Trial in 1996. Data     were collected for yield (bushels per acre), maturity (date), lodging     score     (1 = completely upright, 9 = completely prostrate), plant height (cm.),     sudden death syndrome field score (1 = no visible symptoms, 9 = severe     leaf symptoms), and stem canker field score (1 = no symptoms, 9 = severe     leaf and plantsymptoms). Data are summarized in the following table.            Yield                Maturity                     Lodging                         Height                             SDS Score                                  St canker     Variety            Ave 15                Ave 3                     Ave 5                         Ave 8                             Ave 1                                  Ave 1     __________________________________________________________________________     S73-Z5 43.7                10-14                     2.7 95  1.0  1.5     S 75-55            44.0                10-16                     2.7 96  4.8  1.5     Hz6686RR            35.5                10-14                     3.0 99  6.1  1.0     Hz6686 36.8                10-13                     3.7 88  6.7  1.0     Stonewall            38.8                10-15                     4.4 92  4.3  1.5     Pio. 9761            42.4                10-16                     2.6 91  2.9  1.0     LSD .05            4.6 5    3.3  7  1.7  1.9     __________________________________________________________________________

DEPOSIT INFORMATION

A deposit of the soybean seed of this invention is maintained by Novartis Corporation, 3054 Cornwallis Road, Research Triangle Park, N.C., 27709. Access to this deposit will be available during the pendency of this application to persons determined by the Commissioner of Patents and Trademarks to be entitled thereto under 37 C.F.R. § 1.14 and 35 U.S.C. § 122. Upon allowance of any claims in this application, all restrictions on the availability to the public of the variety will be irrevocably removed by affording access to a deposit of at least 2,500 seeds of the same variety with the American Type Culture Collection, 10801 University Blvd, Manassas, Va., ATCC Accession Number 203504. 

What is claimed is:
 1. A soybean seed designated S73-Z5 (ATCC Accession Number 203504).
 2. A plant or plants of the soybean cultivar designated S73-Z5 produced by growing the seed of claim
 1. 3. Pollen of the plant of claim
 2. 4. Ovule or ovules of the plant of claim
 2. 5. A soybean plant with all of the physiological and morphological characteristics of the soybean plant of claim
 2. 6. Tissue culture of the plant of claim
 2. 7. A soybean plant regenerated from the tissue culture of claim 6 wherein the regenerated soybean plant has all of the physiological and morphological characteristics of a plant grown from a soybean seed designated S73-Z5.
 8. A method to produce a hybrid soybean seed comprising the steps of:a) planting in pollinating proximity seeds of soybean cultivar S73-Z5 (ATCC Accession Number 203504) and another soybean cultivar; b) cultivating soybean plants resulting from said seeds until said plants bear flowers; c) emasculating the plants of either one or the other soybean cultivar; d) inducing cross pollination to occur between said soybean cultivars; and e) harvesting seeds produced on said emasculated plants of the cultivar line.
 9. A first generation (F₁) hybrid soybean plant produced by growing said hybrid soybean seed of claim
 8. 